Vehicle drivetrain with interaxle differential and method for drivetrain operation

ABSTRACT

Systems and methods for an interaxle differential (IAD) are provided. In one example, the IAD comprises a locking assembly that includes a friction clutch, the friction clutch includes a clutch pack that comprises plurality of plates configured to engage and disengage to inhibit and permit speed differentiation between a first axle differential and a second axle differential. The IAD further includes a supply lubrication passage that comprises an inlet that receives a lubricant from an enclosure surrounding an input gear of an axle differential and a first outlet flowing the lubricant to a gear coupled to the clutch pack.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional ApplicationNo. 62/981,917, entitled “VEHICLE TRANSMISSION COMPONENT, SYSTEM, ANDMETHOD” filed on Feb. 26, 2020. The entire contents of theabove-referenced application are hereby incorporated by reference intheir entirety for all purposes.

BACKGROUND AND SUMMARY

Vehicle drivetrains under certain conditions may experience drive axleslip in tandem axles, which may adversely impact vehicle handling. Toprevent slip, some interaxle differentials (IADs) have included dogclutches that lock the differential to increase traction, under someconditions. Constraints may be placed on the IAD locking device whichlimit the window in which IAD locking and unlocking functionality canoccur.

IADs may further include lubrication systems to reduce component wearand increase IAD longevity. U.S. Pat. No. 9,816,603 B2 to Hayes et al.teaches an IAD lubrication system which routes lubricant to bearingscoupled to an input shaft. The lubricant is routed via passagesintegrated into various shafts in the IAD. The IAD system furtherincludes a lock collar with sets of teeth that engage and disengage tolock and unlock the IAD.

The inventors have recognized drawbacks with the IAD system taught byHayes as well as other IAD systems with locking capabilities. Forinstance, the IAD locker, embodied as a dog clutch, may be susceptibleto wear and improper engagement, under certain conditions. Thelubrication system taught by Hayes may not provide targeted amounts oflubricant to certain high wear areas of the differential. Furthermore,the complex routing of Hayes' lubricant passages may increase flowlosses and the likelihood of system degradation. This lubrication systemcomplexity may pose further impediments to achieving lubrication goals.Further, previous IAD locking systems may experience relatively hightorque spike during certain periods of operation that have the potentialto cause component degradation. Facing these challenges, the inventorsdeveloped an IAD. The IAD, in one example, includes an input interfaceconfigured to receive power from a prime mover. The IAD furthercomprises a locking assembly that includes a friction clutch. Aplurality of plates in the clutch are configured to disengage and engageto inhibit and permit speed differentiation between a first axledifferential and a second axle differential. The first axle differentialincludes a bevel gear coupled to a case. Further, the supply lubricationpassage includes an inlet that receives a lubricant from an enclosuresurrounding the bevel gear and an outlet flowing the lubricant to a gearcoupled to the clutch pack. In this way, the clutch pack is efficientlylubricated using lubricant from the axle differential, therebyincreasing IAD longevity.

In another example, the supply lubrication passage may include a secondoutlet that flows the lubricant to an input bearing and wherein theinput bearing is coupled to an input shaft that extends from the inputinterface. This allows the input bearing and the clutch to beefficiently lubricated using a common passage. Consequently, losses inthe lubrication system may be reduced when compared to a system usingseparate passages for lubricating each component.

In yet another example, the bevel gear may generate splash lubrication.The splash lubricant serves a dual purpose: the first being thelubrication of the axle differential and the second being the deliveryof lubricant to the supply passage inlet. In this way, the supplypassage efficiently gathers lubricant from the axle differential,allowing the components that receive lubricant from the splash system tobe expanded. Consequently, the IAD's longevity may be further increased.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a schematic diagram of a vehicle with an interaxledifferential (IAD).

FIG. 2 shows a perspective view of an example of a drivetrain systemwith an IAD.

FIG. 3 shows a detailed view of the IAD, depicted in FIG. 2.

FIGS. 4A and 4B show cross-sectional views of the IAD, depicted in FIG.3.

FIGS. 5 and 6 show different cross-sectional views of an actuationassembly, in the IAD depicted in FIG. 2.

FIG. 7 shows an exploded view of the actuation assembly, frictionclutch, and associated gearing in the IAD, depicted in FIG. 2.

FIG. 8 shows a cross-sectional view of the friction clutch, shafts, andassociated gears in the IAD, depicted in FIG. 2.

FIG. 9 shows a cross-sectional view of a supply lubrication passage in alubrication system of the IAD, depicted in FIG. 2.

FIG. 10 shows a detailed view of the supply lubrication passage,depicted in FIG. 9.

FIG. 11 shows another cross-sectional view of the supply lubricationpassage, depicted in FIG. 9.

FIG. 12 shows a cross-sectional view of the supply lubrication passageand a return lubrication passage in the IAD lubrication system.

FIG. 13 shows a method for operation of an IAD.

FIG. 14 shows a timing diagram of a use-case IAD control strategy.

FIGS. 2-12 are draw approximately to scale, although other relativedimensions may be used, if desired.

DETAILED DESCRIPTION

Vehicle drivetrain and control method embodiments are described herein.The drivetrain includes an interaxle differential (IAD) that may bedesigned with active locking functionality. The active locking controlstrategy allows the window of locking functionality to be expanded. TheIAD includes, in one example, a friction clutch actuated by an electricmotor to lock and unlock the IAD. A planetary gearset is used in theclutch's actuation assembly as an efficient torque multiplier forengaging and disengaging the friction clutch. The planetary gearsetallows the torque generated by the motor during clutch actuation to bereduced. Consequently, the clutch may be more efficiently actuated andthe system's size and complexity may be reduced. In one example, theplanetary assembly may be non-backdrivable. The non-backdrivableplanetary gearset allows the gears to hold the load from the frictionclutch during clutch engagement. In turn, motor hold torque may not bedemanded during clutch locking operation, thereby increasing theclutch's operational efficiency.

The IAD system may further include a lubrication system that efficientlyroutes lubricant through a supply lubricant passage in the IAD housing.Specifically, the lubricant passage supplies lubricant to a gear coupledto the friction clutch and/or an input bearing in the IAD and the clutchplates. The supply passage may receive lubricant from splash lubricantgenerated by an input gear in an axle differential. In this way, thelubricant flow through the passage may be gathered from an existinglubrication mechanism. Consequently, the components supplied withlubricant by the lubrication system may be expanded without undulyincreasing the system's complexity and/or system losses, for instance.

FIG. 1 shows a schematic depiction of a vehicle with an IAD designed forefficient locking and unlocking operation. FIGS. 2 and 3 show an exampleof a vehicle drivetrain with an IAD with an actuation assembly with aplanetary gearset that allows the IAD's locking mechanism to be lockedan unlocked in a space efficient package. FIGS. 3 and 8 showcross-sectional views of the locking mechanism and actuation assembly inthe IAD. FIGS. 5-6 show a detailed view of the planetary gearset in theIAD. FIG. 7 shows an exploded view of the IAD's actuation assembly andfriction clutch. FIGS. 9-12 show a lubrication system in the IAD thatpassively routes lubricant to the locking clutch and actuation assemblyvia a splash lubrication arrangement in an axle differential. FIG. 13shows a method for automatically locking an IAD based vehicle operatingconditions. FIG. 14 depicts a use-case timing diagram for a clutchlocking sequence in which the motor is initially energized and thende-energized once the clutch reaches engagement.

FIG. 1 shows a schematic diagram of a vehicle 100 that may comprise aprime mover 102 (e.g., an internal combustion engine, an electric motor,combinations thereof, and the like). Thus, in one example, the vehiclemay be a hybrid vehicle which may increase fuel efficiency but addcomplexity to the vehicle. Alternatively, the vehicle may include solelyan internal combustion engine which may reduce vehicle complexity at theexpense of fuel economy, for instance. The vehicle may be a light,medium, or heavy duty type vehicle that may be designed for on-roadand/or off-road travel. The prime mover 102 provides power to adrivetrain 101 that includes a system 104 with an IAD 106. It will beappreciated that the drivetrain may include a transmission.

As described in more detail herein, the IAD 106 may include an actuationassembly 108. The actuation assembly 108 may comprise an electric motor110 which drives a ball ramp actuator 112 via a planetary gearset 114.In turn, the ball ramp actuator 112 engages and disengages sets ofplates in a clutch pack 116 of a friction clutch 118. The electric motor110 may include a rotor electromagnetically interacting with a stator torotate an output shaft in opposing rotational directions. The ball rampactuator 112 may include ramped plates with balls positionedtherebetween. The interaction between the ramps and balls allows theactuator to axial extend and retract an actuation plate, for example. Anenergy source 109 (e.g., battery, capacitor, alternator, combinationsthereof, etc.) may provide electrical energy to the motor 110 forenergization. The transfer of energy from the energy source 109 to themotor 110 is indicated via arrow 111.

The planetary gearset 114 may include a sun gear, planet gears on acarrier, ring gears, etc. The planetary gearset functions as a compacttorque multiplier between the motor and the actuator of the frictionclutch. In this way, the size as well as the electrical energy consumedby the motor to actuate the clutch may be decreased. System efficiencymay be consequently increased. Further, the planetary gearset 114 may benon-backdrivable, such that the clutch can remain engaged and disengagedwithout motor hold torque. Thus, the planetary gearset may hold the loadfrom the friction clutch during clutch engagement. In this way, themotor's energy efficiency may be increased in comparison to systems thatstall the motor to generate clutch hold torque. Designing the planetaryassembly with non-backdrivable functionality may further decrease thechance of motor degradation cause by torque spike events. Specificexemplary arrangements of the gears in the planetary assembly aredescribed in greater detail herein. Exemplary as described herein doesnot give any sort of preferential indication but rather signifies oneamong multiple potential configurations.

The IAD 106 includes a first output 120 (e.g., an output shaft and/orother suitable mechanical attachment that provides power to a first axledifferential 122 in a first drive axle 124). The IAD 106 furtherincludes a second output 126 (e.g., a shaft and/or other suitablemechanical attachment that provides power to a second axle differential128 in a second drive axle 130). To elaborate, the first and seconddrive axles 124, 130 may be included in a tandem drive axle arrangement,in one example. Therefore, in such an example, the tandem drive axlearrangement may not be steerable and may be positioned rearward of asteerable axle which may be a non-drive axle, in some instances.However, in alternate examples, the vehicle may further include a driveaxle which is steerable. The first and second drive axles 123, 130include axle shafts 132, 134, (e.g., half shafts) respectively, whichare rotationally coupled to drive wheels 136, 138. In this way, thepower path through the drivetrain may be routed to drive wheels.

Due to the schematic illustration in FIG. 1, certain structural detailsmay be shown at a high level. However, the IAD may have additionalstructural features that are depicted in greater detail with regard toFIGS. 2-12. For instance, the IAD housing may be directly attached to ahousing of the first axle differential.

The first and second axle differentials 122, 128 may be configured topermit speed differentiation between the corresponding axle shafts(e.g., axle half shafts). To achieve this functionality, thedifferentials may include an input gear, a case, spider gears, sidegears, and the like, in one example. Other types of differentials suchas epicycle differentials, have been contemplated. Further in someexamples, at least one of the axle differentials may include lockingfunctionality. The axle differential locker(s) may be electronic orhydraulic type locking device(s), for instance. Alternatively, inanother example, the axle differential lockers may be omitted from thedrivetrain due to the increased traction provided by the IAD lockingdevice. Consequently, system complexity and cost may be reduced.

The system 104 may further include a lubrication assembly 140. Theworking fluid in the lubrication system may be a suitable lubricant suchas natural and/or synthetic oil. The lubrication assembly 140 includes asupply lubricant passage 142. The supply lubricant passage 142 mayinclude an inlet 143 that may receive lubricant (e.g., splash lubricant)from a gear (e.g., bevel gear) in the first axle differential 122. Thesupply lubricant passage 142 may include a first outlet 144 and a secondoutlet 145. The first outlet 144 may supply lubricant to a gear coupledto the friction clutch 118. Further, the second outlet 145 may supplylubricant to a bearing 146 (e.g., input bearing) coupled to an inputshaft 147. The shaft may extend from an input interface such as a yokewhich receives power from the prime mover. The lubrication assembly 140may further include a return passage 148 which routes lubricant back toa sump 149 in the first axle differential 122.

A control system 150 with a controller 152 may be incorporated in thevehicle 100. The controller 152 includes a processor 154 and memory 156.The memory 156 may hold instructions stored therein that when executedby the processor cause the controller 152 to perform the variousmethods, control strategies, lubrication techniques, etc., describedherein. The processor 154 may include a microprocessor unit and/or othertypes of circuits. The memory 156 may include known data storage mediumssuch as random access memory, read only memory, keep alive memory,combinations thereof, etc. Further, the memory 156 may includenon-transitory memory.

The controller 152 may receive vehicle data and various signals fromsensors positioned in different locations in the vehicle 100 and thedrivetrain system 104, indicated at 158. The sensors may include a motorposition sensor 160, shaft speed sensors 162, 164, wheel speed sensors166, clutch position sensor 168, etc. The controller 152 may sendcontrol signals to controllable components, indicated at 169. Thecontrollable components may include the motor 110. For instance, thecontroller 152 may send signals to the motor 110 to adjust therotational speed, torque, and/or direction of motor rotation, indicatedvia arrows 170. The controller 152 may send signals to othercontrollable components, such as the axle differentials 122, 128, theprime mover 102, etc. Alternatively, the controller may solely controlcomponents in the drivetrain such as the actuation assembly (e.g., theelectric motor). Additionally or alternatively, a vehicle electroniccontrol unit (ECU) may be provided in the vehicle to control otheradjustable components such as the prime mover (e.g., engine). It will beappreciated that the motor may be controlled to lock and unlock the IAD.The control system 150 and specifically the controller 152 with thememory 156 and processor 154 may therefore be configured to carry outthe control techniques elaborated upon herein with regard to FIGS.13-14, for instance.

The vehicle 100 may include an input device 172 (e.g., a button, aswitch, a touch panel, a touch interface, and the like). The inputdevice 172, responsive to driver input, may generate a mode request thatindicates a desired state (e.g., locked or unlocked state) of the IAD.Additionally or alternatively, IAD locking may be initiatedprogrammatically taking into account vehicle operating conditions suchas wheel speed, wheel slip, and/or ambient temperature. The input devicemay be located in a vehicle cabin (e.g., vehicle dash), in some cases.However, in other examples, the input device may be omitted from thevehicle and the controller may provide an automatic and active IADlocking control strategy.

An axis system is shown in FIG. 1 as well as FIGS. 2-12 to establish acommon frame of reference. In one example, the z-axis may be parallel toa gravitational axis, the x-axis may be a lateral axis, and the y-axismay be a longitudinal axis. However, other orientations of the axes maybe used, in other examples.

FIG. 2 shows a perspective view of an example of a drivetrain system200. The system 200 illustrated in FIG. 2 may be an example of thesystem 104 depicted in FIG. 1. As such, the systems may share commonstructural and/or functional features. The drivetrain system 200includes an IAD 202 and may further include a first axle differential204 and a second axle differential 206. The axle differentials may forma portion of drive axles that comprise axle shafts rotationally coupledto drive wheels. Further, in one example, the axles may be beam axles inwhich the wheels are connected via a continuous structure (e.g., beam,shaft, and the like). A mechanical assembly 208 with shafts 210, joints212, and/or other suitable mechanical components may deliver power fromthe IAD 202 to the second axle differential 206. The joints 212 enablearticulation between the drive axles and may be U-type joints. However,other types of joints for transferring rotational energy between thedrive axles, have been contemplated.

The IAD 202 may include a housing section 214 that at least partiallyencloses shafts, gears, and the like that facilitate the power transferand the speed differentiation between the speed of the shafts coupled tothe first and second axle differentials. The IAD may further include ahousing section 216 that at least partially encloses an actuationassembly 218 and/or a clutch. The housing sections 214, 216 may beremovably coupled via attachment devices 217 (e.g., bolts). However,other attachment techniques such as welding have been contemplated. Aspreviously discussed, the clutch is designed to inhibit and allow speeddifferentiation between two drive axles. In this way, vehicle tractionmay be increased during selected conditions to enhance vehicle handling.Bolts or other suitable attachment devices may be used to removablyattach the housing sections to one another.

The actuation assembly 218 includes an electric motor 220. An input yoke222 or other suitable mechanical component may be provided in the IAD toserve as an interface with an engine, electric motor, or other suitableprime mover. The housing section 214 is removably attached to a housing224 of the first axle differential 204. Specifically, bolts 226 and/orother suitable mechanical attachment devices may extend through flangesin the housing section 214 and the housing 224 to facilitate theremovable mechanical attachment. In this way, the axle differential maybe compactly incorporated into the drivetrain, although less spaceefficient arrangements have been envisioned.

Housing sections 228, 230 of the second axle differential 206 arefurther depicted in FIG. 2. The housing of both the first and seconddifferential may have a banjo shape. However, alternative differentialhousing layouts may be used, in other examples.

FIG. 3 shows a detailed view of the IAD 202. The input yoke 222,electric motor 220, housing section 214, and housing section 216 areagain shown. A gear 300 (e.g., an input gear such as a ring gear or abevel gear) of the first axle differential 204 is shown along with anoutput shaft 302 that may be rotationally coupled to the second axledifferential 206 by, for example, the shafts and joints, depicted inFIG. 2.

The electric motor 220 may be arranged above the input yoke 222 and mayextend axially away from the housing section 216. Other motorarrangements have been contemplated which may be determined based onpackaging constraints imposed by other vehicle components such as theframe, motive power source (e.g., engine and/or drive motor), and thelike. The motor 220 may further be laterally positioned between an inputshaft and a side shaft in the IAD 202, in one example. A rotational axis304 of the input shaft, a rotational axis 306 of the side shaft, and arotational axis 308 of the motor, are provided for reference. The sideshaft may enable rotational energy transfer to the gear 300 in the firstaxle differential 204 from the IAD gearing. Thus, the side shaft mayfunction as an output shaft. This motor arrangement may increase IADspace efficiency. However, other motor positions may be used, in otherexamples.

FIG. 3 shows cutting planes 4A, 4B that correspond to thecross-sectional views illustrated in FIGS. 4A and 4B. FIG. 3additionally, shows cutting plane 9, 11, 12 that correspond to thecross-sectional views illustrated in FIGS. 9, 11, and 12, respectively.

FIGS. 4A and 4B show different cross-sectional views of the IAD 202associatively arranged in relation to one another for structuralcontext. Specifically, FIG. 4A shows a cross-section of the electricmotor 220 and a planetary gearset 400 included in the actuation assembly218. The motor 220 and the planetary gearset 400 may be coaxial.Further, the rotational axis 308 of the motor 220 and the planetarygearset 400 may be parallel to and positioned vertically above an inputshaft 402, shown in FIG. 4B. In this way, the actuation assembly may bespaced efficiently packaged in the IAD. However, other relativepositions of the motor and planetary gearset may be used.

Continuing with FIG. 4A, the planetary gearset 400 may be a self-lockingplanetary gearset that is designed to be non-backdrivable. As describedherein, non-backdrivability denotes that power applied to the gearset'soutput from downstream components (e.g., the ball ramp actuator andlocking clutch) may not travel through the gearset back to its input.Conversely, the sun gear may be rotated in opposing directions whichdrive rotation of the planetary assembly's output (e.g., the second ringgear). Thus, the gearset may hold loads from downstream component suchas loads experienced during clutch engagement. This load holdingfeature, allows motor hold torque during clutch engagement to beavoided, if desired. As indicated above, the planetary gearset 400 mayprovide rotational input to a ball ramp actuator 404, which is depictedin FIG. 4B.

FIG. 4B further shows a friction clutch 406 and the ball ramp actuator404 in the actuation assembly 218 of the IAD 202. The friction clutch406 may include a clutch pack 408 with different sets of plates thatfrictionally engage and disengage one another. Each set of plates mayinclude a plurality of plates.

The ball ramp actuator 404 may include plates 410, 412 with ramps thathave balls 414 positioned therebetween. Rotation of one of the plate 412in opposing rotational directions may axially extend and retract theplate. In this way, rotational motion may be transformed into lineartranslational motion. The plate 412 may receive rotational input fromthe planetary gearset 400 (e.g., a ring gear in the planetaryarrangement), shown in FIG. 4A.

A bearing 416 (e.g., thrust bearing) may be coupled to the input shaft402 and the ball ramp actuator 404 and constrain rotation of thesecomponents. As described herein, a bearing may include roller elementsand races that allow the bearing to constrain rotation of thecomponent(s) to which it is attached. A helical gear 418, spider 422(e.g., spider body), and pinon gears 424 (e.g., spider gears) on thespider are further illustrated in FIG. 4B. The spider 422 isrotationally coupled to the input shaft 402.

The helical gear 418 may include teeth 423 on an outer surface that aredesigned to mesh with teeth on the side shaft that comprises a piniongear coupled to the input gear in the first axle differential. Asdescribed herein gears which transfer power therebetween includesmeshing teeth that facilitate rotational energy transfer between thecorresponding gears. The helical gear may further include teeth 426 thatfunction as a side gear and mesh with the pinion gears 424. In the IAD,another side gear 428 may mesh with the pinion gears 424.

The clutch 406 may rotationally connect and disconnect the helical gear418 to the input shaft 402. In this way, the IAD may be locked anunlocked. Specifically, when the clutch 406 is disengaged, a portion ofthe IAD power path may travel from the input shaft 402 to the spider422, from the spider to the pinion gears 424, from the pinions to thehelical gear 418 via the side gear teeth 426, and from the helical gearto the first axle differential by way of the side shaft (e.g., offsetshaft) and gear arrangement. Further, in the clutch's disengagedconfiguration, a portion of the power path travels from the pinion gears424 to the side gear 428, and from the side gear to the output shaft302, shown in FIG. 3. In this way, the IAD is designed to permit speeddifferentiation between the drive axle outputs while power is dividedbetween the drive axles.

Conversely, while the clutch is engaged, a portion of the IAD power pathmay travel from the input shaft 402 to the helical gear 418, and fromthe helical gear to the first axle differential via the offset shaftarrangement. Further while the clutch is engaged, the spider 422 andside gear 428, correspondingly, rotate in unison with the helical gear418. This prevents speed differentiation between the drives axles toprovide a fixed power split. In this way, the IAD may be locked andunlocked to modulate vehicle traction, thereby enhancing vehiclehandling in a variety of operating environments.

Another bearing 430 is coupled to the side gear 428. Further, it will beunderstood that the side gear 428 may be rotationally attached to theoutput shaft 302, shown in FIG. 3. The output shaft 302 may be coupledto the second axle differential 206, depicted in FIG. 2. The housingsections 214, 216 that at least partially enclose the actuation assemblyand friction clutch are further depicted in FIG. 4B. The housingsections 214, 216 may be configured to retain a lubricant therein whichis delivered from lubrication passages, described in greater detailherein with regard to FIGS. 9-12.

FIGS. 5 and 6 show cross-sectional views of the electric motor 220 andplanetary gearset 400 in the actuation assembly 218 of the IAD. Themotor 220 shown in FIGS. 5 and 6 is positioned in a different locationthan the previous figures. The motor's location may be selected based onpackaging constraints, motor size, and/or other end-use designparameters.

The planetary gearset 400 may be a two-stage planetary gearset. Theratio of the planetary gearset may be selected to provide a desireddegree of torque multiplication for friction clutch actuation. Expectedloading of the IAD may be taken into account when selecting theplanetary gearset's ratio.

An output shaft 500 of the motor 220 may be rotationally coupled (e.g.,directly coupled) to a sun gear 502 in the planetary gearset 400. Thesun gear 502 therefore may serve as an input of the planetary assembly.A first ring gear 504 and a second ring gear 506 are further shown inFIGS. 5-6. The first and second ring gears 504, 506 include teeth on aninner surface that mesh with gear teeth in a first and second set ofplanet gears 508, 510, respectively.

The sets of planet gears 508, 510 may not be equivalent in size, in oneexample. For instance, the planet gears 508 may be smaller than theplanet gears 510 or vice versa. In other examples, the sets of planetgears may be equivalently sized. The size of the gears in the planetarygearset may be selected to achieve a desired ratio that allows forefficient friction clutch actuation. The second ring gear 506 mayfurther include teeth 512 on an outer surface. Further, the teeth 512may mesh with teeth 513 in the plate 412 of the ball ramp actuator. Inthis way, the second ring gear may serve as the output of the planetarygearset. However, other planetary gearset constructions may be used, inalternate examples. The first ring gear 504 may be held stationary withregard to a housing 514 while the second ring gear 506 is allowed torotate and drive the ball ramp actuator 404, shown in FIG. 4B.

The planet gears 508, 510 may reside on a carrier 516 that rotates inrelation to the housing 514 during clutch actuation. However, planetarylayouts with a distinct carrier for each set of planet gears may beused, in other examples. A planetary carrier covers 518, 520 may becoupled to the carrier 516. In turn, bearings 522, 524 may be coupled tothe covers 518, 520. The bearings 522, 524 and cylindrical sections ofthe carrier covers 518, 520 reside in recesses in the housing 514. Thehousing 514 further includes an opening 526 that allows the plate 412 ofthe ball ramp actuator to extend therethrough and mesh with the secondring gear 506.

FIG. 7 shows an exploded view of the actuation assembly 218 and asection 700 of the IAD including the friction clutch 406, among othercomponents. The input yoke 222 is again shown. A nut lock 702 designedto attach the input shaft 402 to the yoke may be further provided in theIAD. A slinger 704, seal 706, and/or bearing adjuster 708 may be furtherincluded in the IAD. These components may protect the bearing 416 fromcontamination as well as provide bearing preload adjustment.

Further in FIG. 7, the actuation assembly motor 220 with its outputshaft 500 is again shown. A planetary cover 712 may be included in theactuation assembly to prevent debris from contaminating the planetaryassembly.

The planetary gearset 400 may be a two-stage arrangement, as previouslyindicated. In the two-stage gearset embodiment, the gearset may includethe first ring gear 504, the second ring gear 506, the sun gear 502, thefirst set of planet gears 508 on the carrier 516 (e.g., the carriershafts), the second set of planet gears 510 on the carrier. The secondring gear 506 may include teeth 512 on an outer surface that functionsas the planetary assembly's output, as previously discussed. This outputmay be coupled to teeth 513 in the plate 412 of the ball ramp actuator404. Conversely, the sun gear 502 may function as the planetarygearset's input. The planetary gearset 400 may further include bearings714, 716, 718 (e.g., needle roller bearings). The cover 518 (e.g.,carrier holding cover) and the cover 520 (e.g., carrier locking cover)that may be included in the planetary gearset are again illustrated.

FIG. 7 further depicts the housing section 216 that may include aportion 719 that at least partially encloses the planetary arrangement,when assembled. The housing may further include a portion 721 that atleast partially encloses the ball ramp actuator 404 and the frictionclutch 406, when assembled. The housing portion 719 may be axiallyoffset from the rotational axis 304 of the input shaft 402.Specifically, the planetary arrangement may be axially offset andpositioned vertically above the ball ramp and friction clutch for moreefficient component packaging. Further, positioning the planetaryassembly and the electric motor above the other portions of the IAD maymake them less susceptible to degradation from road debris, forinstance.

As previously discussed, the planetary gearset 400 may benon-backdrivable. Thus, when torque is applied to the second planetarygear from friction clutch via the ball ramp actuator, the torque may notbe transferred to the planetary gearset's input (e.g., the sun gear).Thus, the planetary assembly may be solely drivable from the sun gear.In one specific example, the planetary assembly may be a wolfram typeplanetary gearset. In this way, the planetary gearset may hold the loadfrom the clutch during engagement. This allows the motor to bede-energized after the clutch transitions into its engaged position andavoids motor degradation that may be caused by torque spikes duringclutch engagement. Consequently, energy may be conserved in theactuation system when compared to systems that rely on the motor torqueto sustain clutch engagement.

The bearing 416 may be coupled to the input shaft 402 and therefore maybe referred to as an input bearing. Further, the ball ramp actuator 404may further include the plate 410. The plates in the actuator includeramped surfaces that interact with balls to axial extend and retract theactuator. The plate extension and retraction, frictionally engages anddisengages plates in the clutch pack 408 of the friction clutch 406.Another bearing 722 (e.g., needle roller bearing), a bearing 723 (e.g.,needle roller bearing), a retaining spring 724, a bearing 726 (e.g., athrust needle roller bearing), a spring 728 (e.g., wave washer), abearing 730 (e.g., needle roller bearing), and a spring 732 (e.g., wavespring) may be included in the IAD. These components may function toconstrain rotation of components in the friction clutch and allow theball ramp to retract. However, one or more of the springs and bearingsmay be omitted from the IAD, in other examples. The friction clutch 406may include a clutch plate 734, clutch discs 736, 738, and outer clutchring 740. The clutch discs 736, 738 may be sets of clutch discs thatfrictionally engage and disengage one another during clutch operation.Further, the helical gear 418 may be coupled to the outer clutch ring740 to enable the clutch to permit power transfer to the helical gearwhen in an engaged configuration.

The spider 422 with the pinion gears 424 is again shown along with theside gear 428. Clips and/or other suitable mechanical attachment may beused to retain the pinion gears on the spider while allowing the pinionsto rotate on the spider shafts during certain conditions. A cover 742that partially encloses the spider 422 may be further included in theIAD along with a spacer 744 for bearing preload. The spider may rotatein tandem with the input shaft 402. While the IAD is unlocked, as thespider rotates, the pinions rotate thereon and drive the side gear 428to enable speed differentiation between the outputs that deliver powerto the axle differentials.

FIG. 8 shows another cross-sectional view of the IAD 202. The input yoke222, input shaft 402, friction clutch 406, helical gear 418, side gear428, and pinion gears 424 are again illustrated. FIG. 8 further depictsa first output shaft 302. Bearings such as needle bearings may bepositioned between the side gear 428 and the input shaft 402 to enableindependent rotation therebetween. The first output shaft 302 may becoupled to the side gear 428 via a splined interface 801 and/or othersuitable mechanical attachment technique. Additionally, the output shaft302 may be rotationally coupled to the second axle differential 206shown in FIG. 2 by way of the shafts 210 and joints 212, for instances.An output interface 802 (e.g., yoke, joint, gear, combinations thereof,etc.) on the output shaft 302 may provide mechanical attachment to thedownstream components. Bearings 804 facilitate rotation of the outputshaft 302.

FIG. 9 illustrates a cross-sectional view of a lubrication system 900.The lubrication system 900 may include a supply lubrication passage 902.The passage 902 has an inlet 904. Specifically, in one example, theinlet 904 may receive a lubricant from an enclosure 906 in the firstaxle differential 204. To elaborate, the gear 300 (e.g., bevel gear) maysupply splash lubricant to the inlet 904. This lubricant flow isindicated via arrow 908. The gear's splash lubrication may further bedirected to side gears, spider gears, etc., in the first axledifferential. In this way, the splash lubrication may serve a dual-use(differential lubrication and the supply of lubricant to the passage902). Consequently, the axle differential components and the IADcomponents can be efficiently lubricated using a compact arrangement.

The supply lubrication passage 902 may be angled downward in relation tothe gravitational axis. For instance, the slope of the passage may begreater than or equal to 5 degrees as measured from a horizontal axis.In this way, the lubricant flow may be gravity driven. As such, a pumpmay not be used to flow lubricant through the passage, therebydecreasing system complexity. However, in other examples, thelubrication system may use a pump which may decrease system efficiency.

The supply lubrication passage 902 may further include a first outlet910 and/or a second outlet 912 shown in greater detail in FIG. 10, inone example. The first outlet 910 may supply lubricant to the helicalgear 418, shown in FIG. 8. Further, the first outlet may laterallyextend away from the body of the passage to flow lubricant to a desiredhelical gear location. The second outlet 912 may supply lubricant to theinput bearing 416, shown in FIG. 8. In this way, component wear in theactuation assembly may be reduced, thereby extending the assembly'slifespan.

Continuing with FIG. 9, the supply lubrication passage 902 may bepositioned vertically below the electric motor 220 but vertically abovethe side shaft 1001, shown in FIG. 11, for compact lubricant routing.However, other lubricant passage contours have been envisioned.

The supply lubricant passage 902 includes a section 914 that laterallyextends toward the bearing 416, shown in FIG. 8. This section may be arib which structurally reinforces the IAD housing. In this way, thelubricant may be efficiently routed through the housing without undulyimpacting housing strength.

FIG. 10 includes a detailed illustration of the lubrication passage 902in the lubrication system 900 with the surrounding IAD housing omittedto reveal the passage's contours. The passage 902 may include a manifold1000 which distributes lubricant to the first outlet 910 and the secondoutlet 912. The first outlet 910 is shown adjacent to the helical gear418, which facilitates lubrication thereof. The inlet 904 of the passage902 which receives splash lubricant from the gear 300 is againillustrated in FIG. 10. The gear 300 is shown meshing with a gear 1003on the side shaft 1001. In this way, the first axle differential mayreceive power from the IAD during drivetrain operation. Thus, the sideshaft 1001 may function as an output shaft of the IAD. A gear 1005 thatmeshes with the helical gear 418 is further illustrated in FIG. 10 alongwith the friction clutch.

The lubrication passage 902 may be positioned laterally between the sideshaft 1001 and the input shaft 402. In this way, the passage may bespace efficiently routed through the IAD's outer housing. Thelubrication passage 902 may further be located above the side shaft 1001and the input shaft 402 to allow the flow through the passage to begravity driven, in one example.

The lubrication passage 902 may include planar sidewalls 1002 and a basesurface 1004. This arrangement may enable the lubricant to be moreefficiently collected at the passages inlet. However, other contourshave been envisioned. The lubrication passage 902 may decrease incross-sectional area from the inlet 904 to the second outlet 912. Inthis way, the size of the lubricant passages may be tailored to achievea desired amount of lubricant flow without unduly impacting thehousing's structural integrity.

FIG. 11 shows a detailed view of the supply lubrication passage 902 andspecifically the second outlet 912. As shown, the outlet 912 opens intothe input bearing 416. However, in other examples, the outlet 912 mayopen in a region that is adjacent to the clutch pack. Further, the inputbearing 416 may be contoured to direct the lubricant to plates in theadjacent clutch pack. For instance, the bearing may include lubricantoutlets that are axially aligned that open adjacent to the clutch pack.

FIG. 12 again shows the lubrication system 900 with the supplylubrication passage 902 in the IAD 202. The supply lubrication passage902 is again shown extending through the housing 214. The lubricationsystem 900 may further include a return lubrication passage 1200. Thereturn lubrication passage 1200 is positioned vertically below thesupply lubrication passage 902. Further, the lubrication passage 1200flows lubricant back to a sump 1202 in the enclosure 906. From the sump,the lubricant is picked up via the gear 300, shown in FIG. 10, whichinitiates the splash lubrication. The return passage 1200 thereforeallows for efficient circulation of the lubricant in the IAD. The flowof lubricant through the return lubrication passage may be gravitydrive, in one example. Consequently, the system's energy efficiency maybe increased when compared to systems using lubricant pumps to generatelubricant flow. The section 914 of the supply lubrication passage 910that extends toward the input bearing is again shown in FIG. 12.

FIGS. 1-12 show example configurations with relative positioning of thevarious components. If shown directly contacting each other, or directlycoupled, then such elements may be referred to as directly contacting ordirectly coupled, respectively, at least in one example. Similarly,elements shown contiguous or adjacent to one another may be contiguousor adjacent to each other, respectively, at least in one example. As anexample, components laying in face-sharing contact with each other maybe referred to as in face-sharing contact. As another example, elementspositioned apart from each other with only a space there-between and noother components may be referred to as such. As yet another example,elements shown above/below one another, at opposite sides to oneanother, or to the left/right of one another may be referred to as such,relative to one another. Further, as shown in the figures, a topmostelement or point of element may be referred to as a “top” of thecomponent and a bottommost element or point of the element may bereferred to as a “bottom” of the component, in at least one example. Asused herein, top/bottom, upper/lower, above/below, may be relative to avertical axis of the figures and used to describe positioning ofelements of the figures relative to one another. As such, elements shownabove other elements are positioned vertically above the other elements,in one example. As yet another example, shapes of the elements depictedwithin the figures may be referred to as having those shapes (e.g., suchas being circular, straight, planar, curved, rounded, chamfered, angled,or the like). Further, elements shown intersecting one another may bereferred to as intersecting elements or intersecting one another, in atleast one example. Further still, an element shown within anotherelement or shown outside of another element may be referred as such, inone example.

FIG. 13 shows a method 1300 for operation of an IAD in a drivetrain. Themethod 1300 may be implemented by the drivetrains and IADs describedabove with regard to FIGS. 1-12, in one example, or may be implementedby another suitable drivetrain and IAD, in another example. Furthermore,the method 1300 may be implemented by a controller including a processorand memory, as previously discussed.

At 1302, the method includes determining operating conditions. Theoperating conditions may include vehicle speed, axle differentialspeeds, ambient temperature, wheel speeds, vehicle traction, and thelike. The operating conditions may be determined via sensor inputs,modeling, look-up tables, and/or other suitable techniques.

Next at 1304, the method includes determining whether or not to lock theIAD. This determination may be automatically carried out without anoperator request to lock the IAD, in one example. Operating conditionsthat may be taken into account when determining the IAD's locking statemay include vehicle speed and the speeds of both the first and seconddrive axle differentials. For instance, when the vehicle speed is lowerthan a threshold value (e.g., 64 kilometers per hour (km/h), 70 km/h, or80 km/h) and the difference between the axle differential speeds exceedsa threshold variance, it may be determined. The speed variance betweenthe axle differential may be indicative of drive axle slip oranticipated drive axle slip. In other examples, the IAD may be lockedbased on one or more vehicle traction conditions. These tractionconditions may include operating conditions such as wheel slip, ambienttemperature, engine speed, driver requested torque (e.g., acceleratorpedal position), and the like. In this way, the IAD lock command may begenerated to increase vehicle traction.

If an IAD lock command has not been generated (NO at 1304) the methodmoves to 1306. At 1306, the method includes continuing current IADcontrol strategy. As such, step 1306 may include sustaining the IAD inan unlocked configuration.

On the other hand, if an IAD lock command has been generated (YES at1304) the method moves to 1308. At 1308, the method includes energizingthe motor and sustaining energization until the clutch pack inhibitsspeed differentiation between the axle differentials.

Next at 1310, the method includes de-energize the motor while IADlocking is sustained. To elaborate, the motor may be de-energized oncethe plates in the clutch frictionally engage and locking is achieved. Inthis way, the actuation assembly may efficiently sustain clutchengagement. The use of the non-backdrivable planetary gearset allows forthis motor de-energization.

An IAD unlocking method may further be implemented, in some scenarios.The IAD unlocking method may include determining if the IAD should beunlocked based on one or more vehicle traction conditions such as wheelslip, ambient temperature, engine speed, driver requested torque (e.g.,accelerator pedal position). As such, the IAD may be unlocked whenvehicle traction has surpassed a threshold value. Responsive todetermining that the IAD should be unlocked, the motor may be energizedto rotate the planetary gearset in rotational direction which disengagesthe friction clutch. Once the clutch is disengaged, the motor may againbe de-energized to conserve energy.

Further in one example, a method for lubricating an IAD may be provided.The method may be used to lubricate the IADs described above with regardto FIGS. 1-12 or other suitable IADs. The method may include flowinglubricant through the supply lubrication passage to the first and secondoutlets from the inlet which receives splash lubricant from the axledifferential's input gear. The first outlet directs the lubricant to thehelical gear and the second outlet directs lubricant to the inputbearing. In this way, the IAD locking assembly may be efficientlylubricated to increase IAD longevity and decrease the likelihood ofcomponent degradation in the IAD. The method may further include flowingthe lubricant from the input bearing to plates in the adjacent clutchpack to again decrease clutch wear. The method may further includeflowing lubricant back to the axle differential enclosure through areturn passage. This lubrication flow may be passively driven viagravity and therefore enables lubrication to be carried out withoutenergy consuming components such as lubricant pumps, if desired.

FIG. 14 shows a timing diagram where a use-case control strategy isgraphically depicted. The control strategy may be carried out by thedrivetrain systems and IADs discussed above with regard to FIGS. 1-12,in one example. Alternatively, in other examples, the control strategymay be implemented by other suitable drivetrains and IADs. In each graphof the timing diagram, time is indicated on the abscissa. Althoughspecific numerical values are not indicated on the abscissa, sequentialpoints of interest are designated and time increases from left to right.The ordinates for plot 1402 indicates the IAD lock command (a lock orunlock command) present in the control system. The ordinate for plot1404 indicates voltage delivered to the electric motor, in the IAD'sactuation assembly. The voltage plot is a high level representation ofthe voltage signal and the voltage delivered to the motor may bedelivered via a duty cycle that is less than 100%, for instance.

At t1, an IAD lock instruction is generated. Responsive to generation ofthe lock command, voltage is delivered to the motor to rotate the motorin a first direction to initiate clutch actuation. Once the clutch isengaged and correspondingly inhibiting speed differentiation, thevoltage delivered to the motor is discontinued at t2. Due to thenon-backdrivability of the planetary assembly, the clutch remainsengaged when motor torque is discontinued, thereby conserving energy.

At t3, the IAD is commanded to unlock. Responsive to generation of theunlock command, the voltage is again delivered to the motor to rotatethe motor in a second direction to initiate clutch disengagement. At t4,the motor is de-energized once the IAD unlocks. In this way, the motormay be actively controlled to unlock the clutch. The non-backdrivabilityof the planetary assembly demands active control of the motor forunlocking the clutch.

The technical effect of the drivetrain with the IAD and the method foroperating and lubricating the IAD is to increase vehicle traction,increase IAD efficiency, increase IAD packaging efficiency, and increaseIAD longevity.

The invention will be further described in the following paragraphs. Inone aspect, a drivetrain system is provided that comprises an interaxledifferential (IAD) configured to receive power from a prime mover; amotor configured to drive a planetary gearset; and a ball ramp actuatorconfigured to selectively engage a plurality of plates in a clutch packof a friction clutch in response to receiving rotational input from theplanetary gearset; wherein, in an engaged configuration, the frictionclutch prevents speed differentiation between a first IAD output and asecond IAD output; and wherein the first IAD output is coupled to afirst axle differential and the second IAD output is coupled to a secondaxle differential.

In another aspect, a method for operation of a drivetrain system isprovided that comprises automatically locking an interaxle differential(IAD) based on a speed variance between a first axle differential and asecond axle differential; wherein the IAD comprises: a motor driving aself-locking planetary gearset; and a ball ramp actuator selectivelyengaging a plurality of plates in a clutch pack of a friction clutch inresponse to receiving rotational input from the self-locking planetarygearset; wherein, in an engaged configuration, the friction clutchprevents speed differentiation between a first output shaft and a secondoutput shaft; and wherein the first output shaft is coupled to the firstaxle differential and the second output shaft is coupled to the secondaxle differential.

In yet another aspect, an interaxle differential (IAD) is provided thatcomprises an electric motor rotationally coupled to a sun gear in aself-locking planetary gearset; and a ball ramp actuator configured toselectively engage a plurality of plates in a clutch pack of a frictionclutch in response to receiving rotational input from a ring gear in theself-locking planetary gearset; wherein the ring gear meshes with teethin the ball ramp actuator; wherein, in an engaged configuration, thefriction clutch prevents speed differentiation between a first outputshaft and a second output shaft; and wherein the first output shaft isrotationally coupled to a first axle differential and the second outputshaft is rotationally coupled to a second axle differential.

In yet another aspect, an interaxle differential (IAD) is provided thatcomprises a locking assembly including a friction clutch, wherein thefriction clutch includes a clutch pack that comprises a plurality ofplates configured to engage and disengage to inhibit and permit speeddifferentiation between a first axle differential and a second axledifferential; wherein the first axle differential includes an inputgear; and a supply lubrication passage including: an inlet that receivesa lubricant from an enclosure surrounding the input gear; and a firstoutlet flowing the lubricant to a gear coupled to the clutch pack.

In another aspect, a method for lubricating an interaxle differential(IAD) is provided that comprises flowing a lubricant through a supplylubrication passage that receives, at an inlet, splash lubricant from aninput gear in a first axle differential; and flowing the lubricantthrough a first outlet of the supply lubrication passage to a gearcoupled to a clutch pack; and flowing the lubricant through a secondoutlet of the supply lubrication passage to an input bearing coupled toa shaft that extends from an input interface of the IAD.

In another aspect, an interaxle differential (IAD) is provided thatcomprises a supply lubrication passage traversing a housing, wherein thesupply lubrication passage includes: an inlet that receives splashlubricant from an input gear that is positioned in an enclosure of afirst axle differential; a first outlet supplying the lubricant to agear coupled to a clutch pack in a friction clutch; and a second outletsupplying the lubricant to an input bearing and wherein the inputbearing is coupled to an input shaft that extends from an inputinterface; wherein the clutch pack is actuated by a ball ramp actuatorthat is coupled to a self-locking planetary gear assembly; and whereinthe friction clutch prevents and permits speed differentiation betweenthe first axle differential and a second axle differential.

In any of the aspects or combinations of the aspects, the planetarygearset may be non-backdrivable.

In any of the aspects or combinations of the aspects, the planetarygearset may include a sun gear coupled directly to the motor.

In any of the aspects or combinations of the aspects, the planetarygearset may include a ring gear with teeth on an outer surface that meshwith teeth in the ball ramp actuator.

In any of the aspects or combinations of the aspects, the drivetrainsystem may further comprise a controller including instructions storedin non-transitory memory that when executed by a processor, during afirst operating condition, cause the controller to: automaticallyenergize the motor and rotate the planetary gearset in a firstrotational direction, wherein rotating the planetary gearset in thefirst rotational direction frictionally engages the plurality of platesin the clutch pack; and de-energize the motor after the plurality ofplates frictionally engage and lock the clutch pack.

In any of the aspects or combinations of the aspects, the controller mayinclude instructions stored in the non-transitory memory that whenexecuted by the processor, during a second operating condition, causethe controller to: automatically energize the motor and rotate theplanetary gearset in a second rotational direction, wherein rotating theplanetary gearset in the second rotational direction frictionallydisengages the plurality of plates in the clutch pack; and de-energizethe motor after the plurality of plates frictionally disengage andunlock the clutch pack.

In any of the aspects or combinations of the aspects, the firstoperating condition may be a condition when a speed variance between thefirst and the second axle differentials exceeds a threshold value andthe second operating condition is a condition where the speed varianceis less than the threshold value.

In any of the aspects or combinations of the aspects, the planetarygearset may be a two-stage planetary gearset.

In any of the aspects or combinations of the aspects, the first andsecond axle differentials may be included in a tandem axle.

In any of the aspects or combinations of the aspects, the first andsecond axle differentials may be non-steerable.

In any of the aspects or combinations of the aspects, automaticallylocking the IAD may include rotating the self-locking planetary gearsetin a first rotational direction through energization of the motor untilthe plurality of plates are frictionally engaged and speeddifferentiation between the first and second output shaft is prevented;and after frictional engagement of the plurality of plates,de-energizing the motor.

In any of the aspects or combinations of the aspects, the method mayfurther comprise automatically unlocking the IAD based on a vehicletraction condition.

In any of the aspects or combinations of the aspects, automaticallyunlocking the IAD may include rotating the self-locking planetarygearset in a second rotational direction through energization of themotor until the plurality of plates are frictionally disengaged; andafter frictional disengagement of the plurality of plates, de-energizingthe motor.

In any of the aspects or combinations of the aspects, the self-lockingplanetary gearset may be a non-backdrivable planetary gearset.

In any of the aspects or combinations of the aspects, the IAD mayfurther comprise a controller including instructions stored innon-transitory memory that when executed by a processor, during a firstoperating condition, cause the controller to: de-energize the motorafter the plurality of plates become frictionally engaged in a clutchlocking sequence.

In any of the aspects or combinations of the aspects, the clutch lockingsequence may be automatically implemented without operator input.

In any of the aspects or combinations of the aspects, the IAD mayfurther comprise a controller including instructions stored innon-transitory memory that when executed by a processor, during a firstoperating condition, cause the controller to: energize the electricmotor to rotate the electric motor in a direction that frictionallydisengages the plurality of plates in the friction clutch.

In any of the aspects or combinations of the aspects, the self-lockingplanetary gearset may be a two-stage wolfram planetary gearset.

In any of the aspects or combinations of the aspects, the supplylubrication passage may include a second outlet that flows the lubricantto an input bearing and wherein the input bearing is coupled to an inputshaft that extends from an input interface of the IAD.

In any of the aspects or combinations of the aspects, the input bearingmay be designed to flow the lubricant to the clutch pack.

In any of the aspects or combinations of the aspects, the first outletmay be positioned upstream of the second outlet in the supplylubrication passage.

In any of the aspects or combinations of the aspects, the input gear maygenerate splash lubrication that is directed to a plurality of gears inthe first axle differential and received by the inlet of the supplylubrication passage.

In any of the aspects or combinations of the aspects, the supplylubrication passage may be vertically sloped.

In any of the aspects or combinations of the aspects, the enclosure mayinclude a lubricant reservoir.

In any of the aspects or combinations of the aspects, the IAD mayfurther comprise a return lubrication passage extending between ahousing of the IAD and the enclosure.

In any of the aspects or combinations of the aspects, the IAD mayfurther comprise an electric motor rotationally coupled to a planetarygearset, and a ball ramp actuator receiving rotational input from theplanetary gearset and actuating the clutch pack.

In any of the aspects or combinations of the aspects, the planetarygearset may be non-backdrivable.

In any of the aspects or combinations of the aspects, the method mayfurther comprise flowing the lubricant through the input bearing to aplurality of plates in the clutch pack.

In any of the aspects or combinations of the aspects, the lubricant flowmay not be generated by a pump.

In any of the aspects or combinations of the aspects, the first outletmay be positioned upstream of the second outlet.

In any of the aspects or combinations of the aspects, the gear may be ahelical gear that is rotationally coupled to a set of plates in theclutch pack.

In any of the aspects or combinations of the aspects, the IAD mayfurther comprise a return lubrication passage extending through ahousing of the IAD back to the enclosure.

In any of the aspects or combinations of the aspects, the supply andreturn lubrication passages may be gravity driven.

In any of the aspects or combinations of the aspects, the input bearingmay be coupled to an input yoke that is configured to receive rotationalenergy from a prime mover and wherein the first and the second outletsare positioned vertically below the self-locking planetary gearassembly.

In any of the aspects or combinations of the aspects, the supplylubrication passage may be positioned laterally between an input shaftand an outlet shaft of the IAD.

In another representation, a power divider in a vehicle drivetrain isprovided. The power divider is designed to automatically prevent outputspeed differentiation via a wet friction clutch based on vehicleoperating conditions. The power divider includes an electric motor, aself-locking planetary gearset, and a ball ramp actuator cooperativelyfunctioning to lock and unlock the wet friction clutch.

In yet another representation, a lubrication system in a power divideris provided. The lubrication system passive routes splash lubricant froman axle differential to a helical gear, friction clutch, and input shaftbearing via a sloped passage that traverses a housing of the powerdivider. The sloped passage includes a section that radially extendstowards the input shaft bearing from manifold.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other system hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations, and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations, and/or functions may graphicallyrepresent code to be programmed into non-transitory memory of thecomputer readable storage medium in the control system, where thedescribed actions are carried out by executing the instructions in asystem including the various hardware components in combination with theelectronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. Moreover, unless explicitly stated to the contrary, theterms “first,” “second,” “third,” and the like are not intended todenote any order, position, quantity, or importance, but rather are usedmerely as labels to distinguish one element from another. The subjectmatter of the present disclosure includes all novel and non-obviouscombinations and sub-combinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein.

As used herein, the term “approximately” is construed to mean plus orminus five percent of the range unless otherwise specified.

1. An interaxle differential (IAD), comprising: a locking assemblyincluding a friction clutch, wherein the friction clutch includes aclutch pack that comprises plurality of plates configured to engage anddisengage to inhibit and permit speed differentiation between a firstaxle differential and a second axle differential; wherein the first axledifferential includes an input gear; and a supply lubrication passageincluding: an inlet that receives a lubricant from an enclosuresurrounding the input gear; and a first outlet flowing the lubricant toa gear coupled to the clutch pack.
 2. The IAD of claim 1, wherein thesupply lubrication passage includes a second outlet that flows thelubricant to an input bearing and wherein the input bearing is coupledto an input shaft that extends from an input interface of the IAD. 3.The IAD of claim 2, wherein the input bearing is designed to flow thelubricant to the clutch pack.
 4. The IAD of claim 2, wherein the firstoutlet is positioned upstream of the second outlet in the supplylubrication passage.
 5. The IAD of claim 1, wherein the input geargenerates splash lubrication that is directed to a plurality of gears inthe first axle differential and received by the inlet of the supplylubrication passage.
 6. The IAD of claim 1, wherein the supplylubrication passage is vertically sloped.
 7. The IAD of claim 1, whereinthe enclosure includes a lubricant reservoir.
 8. The IAD of claim 1,further comprising a return lubrication passage extending between ahousing of the IAD and the enclosure.
 9. The IAD of claim 1, furthercomprising an electric motor rotationally coupled to a planetarygearset, and a ball ramp actuator receiving rotational input from theplanetary gearset and actuating the clutch pack.
 10. The IAD of claim 9,wherein the planetary gearset is non-backdrivable.
 11. A method forlubricating an interaxle differential (IAD), comprising: flowing alubricant through a supply lubrication passage that receives, at aninlet, splash lubricant from an input gear in a first axle differential;and flowing the lubricant through a first outlet of the supplylubrication passage to a gear coupled to a clutch pack; and flowing thelubricant through a second outlet of the supply lubrication passage toan input bearing coupled to a shaft that extends from an inputinterface.
 12. The method of claim 11, further comprising flowing thelubricant through the input bearing to a plurality of plates in theclutch pack.
 13. The method of claim 11, wherein the lubricant flow isnot generated by a pump.
 14. The method of claim 11, wherein the firstoutlet is positioned upstream of the second outlet.
 15. An interaxledifferential (IAD), comprising: a supply lubrication passage traversinga housing, wherein the supply lubrication passage includes: an inletthat receives splash lubricant from an input gear that is positioned inan enclosure of a first axle differential; a first outlet supplying thelubricant to a gear coupled to a clutch pack in a friction clutch; and asecond outlet supplying the lubricant to an input bearing and whereinthe input bearing is coupled to an input shaft that extends from aninput interface; wherein the clutch pack is actuated by a ball rampactuator that is coupled to a self-locking planetary gear assembly; andwherein the friction clutch prevents and permits speed differentiationbetween the first axle differential and a second axle differential. 16.The IAD of claim 15, wherein the gear is a helical gear that isrotationally coupled to a set of plates in the clutch pack.
 17. The IADof claim 15, further comprising a return lubrication passage extendingthrough a housing of the IAD back to the enclosure.
 18. The IAD of claim17, wherein the supply and return lubrication passages are gravitydriven.
 19. The IAD of claim 15, wherein the input bearing is coupled toan input yoke that is configured to receive rotational energy from aprime mover and wherein the first and the second outlets are positionedvertically below the self-locking planetary gear assembly.
 20. The IADof claim 15, wherein the supply lubrication passage is positionedlaterally between an input shaft and an outlet shaft of the IAD.